UNBIASED ANALYSIS OF THE FREQUENCY OF BETA-THALASSEMIA POINT MUTATIONS IN A POPULATION OF AFRICAN-AMERICAN NEWBORNS

Objective.-To determine frequency of specific beta-thalassemia alleles in the African-American population prospectively, using newborn scree ning specimens, and to evaluate the need for including these alleles i n screening follow-up programs. Design.-Allele-specific oligonucleotid e tests were developed and used to analyze African-American newborn sc reening specimens for beta-thalassemia point mutations to determine th eir frequency. Direct sequencing of amplified DNA from the dried blood specimens was used to confirm the presence of point mutations. Popula tion.-African-American newborns in Texas. Results.-Allele-specific oli gonucleotides identified five newborn specimens carrying beta-thalasse mia point mutations among 471 specimens from African-American neonates . Direct sequencing of DNA from the dried blood specimens confirmed th at these individuals had a normal and a mutant allele. Five newborn sc reening specimens in which the results of screening and DNA tests were in disagreement (four with FS by screening and AS by DNA, and one wit h FC by screening and AC by DNA) were analyzed for these beta-thalasse mia point mutations and in each case were found to be S/beta-thalassem ia or C/beta-thalassemia compound heterozygotes, respectively. Conclus ions.-Allele-specific oligonucleotides accurately identified newborn s pecimens carrying beta-thalassemia point mutations. Direct sequencing from dried blood specimens confirmed these results. The A(-29)G allele frequency was 0.003, and the C(-88)T frequency was 0.002. These allel es also were observed among positive samples in a neonatal hemoglobino pathy screening program. Therefore, any newborn screening program with a molecular genetic follow-up component must include testing for thes e beta-thalassemia alleles to assure timely and appropriate management for affected infants.